title: The disturbances of endoplasmic reticulum calcium homeostasis caused by increased intracellular reactive oxygen species contributes to fragmentation in aged porcine oocytes.
abstract: Accumulating evidence indicates that cellular and molecular abnormalities occur during oocyte aging, including fragmentation, increases in intracellular reactive oxygen species (ROS), and abnormal Ca(2+) oscillations. The objective of the present study was to characterize the relationships between intracellular ROS, Ca(2+) homeostasis of endoplasmic reticulum (ER), and fragmentation in aged porcine MII oocytes. Prolonged culture (36 h) of porcine oocytes resulted in elevated intracellular ROS level, impaired ER Ca(2+) homeostasis (i.e., Ca(2+) storage, Ca(2+) rising patterns after electroactivation, and the cluster distribution of ER), and increased fragmentation rates. However, when the porcine oocytes were treated with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester), an intracellular Ca(2+) chelator, the fragmentation was significantly inhibited during in vitro aging. In order to pursue the underlying mechanisms, H2O2 and cycloheximide (CHX) were used to artificially increase or inhibit, respectively, the intracellular ROS levels in aged porcine oocytes during in vitro culture. The results demonstrated that incubation of porcine MII oocytes with H2O2 damaged the ER clusters and the Ca(2+) regulation of ER, leading to a high proportion of fragmented oocytes. In contrast, CHX, an intracellular inhibitor of ROS generation, prevented both increase of ROS level and damage of the ER Ca(2+) homeostasis in porcine oocytes during aging, resulting in low fragmentation rate. We conclude that the increased intracellular ROS damaged the ER clusters and ER Ca(2+) homeostasis, resulting in a disorder in ooplasmic free Ca(2+), which caused the fragmentations seen in porcine MII oocytes during aging.
authors.affiliation: National Key Laboratory of Animal Nutrition, Laboratory of Animal Embryonic Biotechnology, College of Animal Science and Technology, National Engineering Laboratory for Animal Breeding, China Agricultural University, Beijing, China.
authors.forename: Da-Wei
authors.initials: DW
authors.lastname: Tang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Fang
authors.forename: Zhen-Xing
authors.initials: ZX
authors.lastname: Liu
authors.forename: Yi
authors.initials: Y
authors.lastname: Wu
authors.forename: Xian-Long
authors.initials: XL
authors.lastname: Wang
authors.forename: Shuan
authors.initials: S
authors.lastname: Zhao
authors.forename: Guo-Cai
authors.initials: GC
authors.lastname: Han
authors.forename: Shen-Ming
authors.initials: SM
authors.lastname: Zeng
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006706:Homeostasis / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects* / Q000502:physiology; D017382:Reactive Oxygen Species / Q000009:adverse effects* / Q000378:metabolism; D013552:Swine / Q000378:metabolism / Q000502:physiology*
chemical_list: D002614:Chelating Agents; D017382:Reactive Oxygen Species; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D002118:Calcium
keywords: calcium; endoplasmic reticulum; fragmentation; porcine oocyte; reactive oxygen species